Caller ID labeled them “unknown,” but Roger Stone said he knew to pick up quickly during those harried months of the 2016 presidential campaign. There would be a good chance that the voice on the other end of the line would belong to his decades-long friend — the restless, insomniac candidate Donald Trump — dialing from a blocked phone number.

Those nocturnal chats and other contacts between the man who now occupies the Oval Office and an infamous political trickster have come under intensifying scrutiny as special counsel Robert S. Mueller III’s investigation bores into whether Stone served as a bridge between Trump and WikiLeaks as the group was publishing hacked Democratic emails.

Mueller’s keen interest in their relationship was laid out in a draft court document revealed this week in which prosecutors drew a direct line between the two men — referring to Stone as someone understood to be in regular contact with senior Trump campaign officials, “including with then-candidate Donald J. Trump.”

The inclusion of the president by name in the draft filing rattled his legal team and indicated how closely the special counsel is scrutinizing what Trump may have learned from Stone about WikiLeaks’ release of emails that prosecutors say were hacked by Russian intelligence operatives.

In recent months, the Trump Organization turned over to Mueller’s team phone and contact logs that show multiple calls between the then-candidate and Stone in 2016, according to people familiar with the material.

The records are not a complete log of their contacts — Stone told The Washington Post on Wednesday that Trump at times called him from other people’s phones.

Stone said he never discussed WikiLeaks with Trump and diminished the importance of any phone records, saying “unless Mueller has tape recordings of the phone calls, what would that prove?”

Stone and WikiLeaks have denied collaborating with each other, and Stone has decried the Mueller investigation as a “political witch hunt” to punish him for supporting Trump.

Trump has told his lawyers — and last week said in written answers to Mueller — that Stone did not tell him about WikiLeaks’ upcoming release and that he had no prior knowledge of it, according to people familiar with his responses.

Roger Stone poses with a poster of Donald Trump from 2000 in his office in Oakland Park, Fla., on April 12, 2017. (Andrew Innerarity/For The Washington Post)

Jay Sekulow, a lawyer for Trump, declined to discuss Trump’s contacts with Stone. “The president has responded to the questions asked by the special counsel,” Sekulow said. “We do not discuss those responses.”

WikiLeaks has been a major focus of the Mueller investigation. In July, prosecutors charged Russian intelligence officers with hacking Democrats and using the group to release stolen material to the public to help Trump defeat Democratic nominee Hillary Clinton.

New details about Stone’s interest in WikiLeaks’ plans emerged this week after one of his associates, conspiracy theorist Jerome Corsi, announced that he had rejected a plea deal offered by Mueller’s team. He provided The Post and other news organizations with a draft filing by prosecutors describing his interactions with Stone — including an Aug. 2, 2016, email in which the right-wing author alerted Stone that he heard WikiLeaks was planning a major release of “very damaging” material.

The next day, Stone had one of his private talks with Trump, Stone said on a 2016 Infowars broadcast first reported by CNN.

In an interview, Stone insisted that the topic of hacked emails was never broached in the Aug. 3 phone call — or in any other communication with Trump.

“It just didn’t come up,” Stone said. “I am able to say we never discussed WikiLeaks. I’m not sure what I would have said to him anyway because it’s all speculation . . . I just didn’t know if it’s true or not.”

Stone, however, sounded much more certain in his public pronouncements at the time, stating confidently that Assange would reveal material that would hurt Clinton’s campaign.

On Wednesday, Stone said he was making such bold statements to “drive media coverage” of the expected WikiLeaks releases.

Stone served as an official adviser in the early stages of Trump’s campaign but left in August 2015. For a few months, they had little contact because of friction over their competing accounts of whether Stone was fired or resigned, Stone said.

“We went through a period of bad feelings,” Stone said.

But eventually the longtime allies were back in touch.

The frequency of their contacts isn’t clear. Stone told the Guardian in November 2016 that they were talking once a week. But Wednesday, he said that statement “might be a little bit of hype” and that they spoke only “occasionally” during the campaign, with their most frequent periods of contact coming at the beginning and the end of the contest.

From January through March 2016, Stone said he had a cellphone number for Trump. But he said the phone number got into too many hands, and Trump’s staff changed it. After that, a pattern developed for their calls, Stone said: Trump would call Stone from a blocked number or from the phones of associates or campaign aides.

“He would initiate the calls,” Stone said. “I didn’t call him.”

Once, Stone said, he answered his iPhone because the caller ID said he was getting a call from Christopher Ruddy, a Trump friend who is the CEO of Newsmax, a conservative television network. But the voice on the line was Trump’s.

“I believe there was one time when he asked me to call Roger,” Ruddy said in an interview Wednesday, adding that he did not believe “there was any discussion related to Russians or improper activities.”

The calls from Trump came at odd hours, Stone said, because Trump “gets almost no sleep.” Trump usually wanted to get a sense of how the campaign was going, Stone said, or just to “touch base.” Stone sometimes offered suggestions, but often he could barely get a word in.

“When Donald Trump calls you, he does most of the talking; you do most of the listening,” Stone said.

A review of the phone contacts that Trump’s team turned over to Mueller showed a series of calls between Stone and Trump over the length of the campaign, according to people familiar with the records.

They spoke from “time to time” during 2016, the people said, but there was no “flurry” of calls at any particular period. A handful of calls were lengthy. The vast majority involved short calls by Stone to Trump’s assistant Rhona Graff that lasted roughly 30 seconds.

Stone said he was usually calling to alert Graff that he was sending her a strategy memo for Trump, which she would print out for him to read since he didn’t use email.

Trump has told some advisers that he no longer talks to Stone, according to people familiar with his statements. But people close to Trump say he has occasionally talked to him in the White House.

Trump is known to use several phones and has placed calls from cellphones that are not logged in the White House switchboard, current and former aides said. He has occasionally asked associates to make calls for him on their phones, they said.

In midsummer 2016, Trump’s allies were keenly interested in what WikiLeaks had planned for the final weeks of the White House race.

On July 22, WikiLeaks had rocked the campaign by releasing more than 50,000 internal Democratic National Committee emails on the eve of the party’s convention. The leak dominated the gathering in Philadelphia and resulted in the resignation of party chairwoman Debbie Wasserman Schultz, a Florida congresswoman.

Three days later, Stone received an email from blogger Charles Ortel, who forwarded a note from Fox News reporter James Rosen. “Am told WikiLeaks will be doing a massive dump of HRC emails relating to the CF in September,” Rosen wrote, referring to the Clinton Foundation. Rosen has declined to comment.

That same day, according to the draft Corsi plea document, Stone reached out to Corsi. “Get to [Assange] [a]t Ecuadoran Embassy in London and get the pending [WikiLeaks] emails . . . they deal with the Foundation, allegedly,” he wrote.

When asked about the email, Corsi at first told prosecutors that he declined Stone’s request and told him that trying to contact WikiLeaks could attract the attention of investigators. But in fact — the draft Mueller document alleges and Corsi acknowledged this week — Corsi forwarded Stone’s request to Ted Malloch, a self-described informal Trump adviser living in London.

Corsi said Stone wanted Malloch to help him undermine the 2016 Democratic candidates.

Meanwhile, on the campaign trail, Trump was also eager to see what other hacked emails might emerge that could help his campaign. On July 27, two days after Stone emailed Corsi, the candidate was asked repeatedly at a news conference about allegations that Russia had hacked the Democratic Party and given the stolen materials to WikiLeaks.

He responded that it was impossible to tell if Russia was behind the attack, but added: “Russia, if you’re listening, I hope you’re able to find the 30,000 emails that are missing,” a reference to emails Clinton sent while secretary of state and then deleted. “I think you will probably be rewarded mightily by our press. Let’s see if that happens. That’ll be next.”

On Aug. 2, 2016, Corsi followed up with Stone.

“Word is friend in embassy plans 2 more dumps,” he wrote, according to the draft filing. “Impact planned to be very damaging. . . . Time to let more than [Clinton campaign chairman John Podesta] to be exposed as in bed w enemy if they are not ready to drop [Clinton]. That appears to be the game hackers are now about.”

Corsi said that email was the product of his deductive reasoning and that he searched his memory and feels confident he had no person connected to WikiLeaks who provided inside information.

“I can take pieces and put them together. I’m not always right. But it’s scary how often I’m right,” Corsi told The Post. “Here I’m stuck with the fact that I figured it out. It turns out I was right. Nobody can believe that I actually did figure it out.”

On Wednesday, Stone said he recently had a cellphone expert extract data from two old iPhones that he used during the campaign. Among the material recovered were text messages that showed Stone asking New York comedian Randy Credico for information about WikiLeaks weeks after he corresponded with Corsi, he said. Stone has long asserted that Credico was his main source of information about Assange’s plans.

Stone has described Corsi, who is best known for his promotion of the false theory that President Barack Obama was not born in the United States, as a researcher who shared information about the business dealings of John Podesta and his lobbyist brother, Tony.

Stone accuses Mueller of “squeezing” Corsi in an attempt to frame him.

“The emails prove nothing,” Stone said, “other than, like every other politico and political reporter in America, I was curious to know what it was that WikiLeaks had.”

Alice Crites in Washington and Karla Adam in London contributed to this report.